Multiple channel mass flow control systems are used to control the flow of fluids through multiple channels, allowing the combination of the fluids from the multiple channels into a shared flow channel in desired proportions. Multiple channel mass flow ratio control systems are used to control the flow of a fluid from a shared flow channel into multiple channels in desired ratios of mass flow. Such systems are used, for example, in semiconductor fabrication systems and other materials processing systems.
A semiconductor fabrication process can involve the delivery of several different gases and gas mixtures in various quantities over several processing steps. Generally, gases are stored in tanks at a processing facility, and gas metering systems are used to deliver metered quantities of gases from the tanks to processing tools, such as chemical vapor deposition reactors, vacuum sputtering machines, plasma etchers, etc. Typically, components such as valves, pressure regulators, mass flow control systems (MFCS), mass flow ratio control systems (FRCS) are included in the gas metering system or in a flow path from the gas metering system to a processing tool.
In certain applications such as semiconductor fabrication applications, space is typically very limited, the systems need to be flexible (e.g., it is desirable that additional flow channels can be easily added to, removed from, or exchanged within existing MFCS or FRCS), and high precision is required. Further, low cost and less complex systems are generally desirable.